Machine to machine (M2M) technology, a combination of wireless communication technologies and information technologies, is a technology that allows machines to directly communicate with each other without human intervention.
M2M communication is also called machine type communication (MTC). An M2M communication system is significantly different from a traditional human to human (H2H) communication system. The M2M communication system has many features of the machine type communication due to the large number of devices, low mobility, low communication traffic, and the like. The M2M communications system is referred to as an MTC communications system in the current Third Generation Partnership Project (3GPP) standard, and in the case of small data transmission (i.e. transmission small data), a short message service (SMS) or an Internet Protocol (IP) packet starts to be used to implement communications between the machines.
When SMS small data or IP packet small data is encapsulated in a tracking area update (TAU) request or a new initial layer-3 message, it needs to be considered how to provide confidentiality protection for the small data part of the initial layer-3 message and for other parameters that require protection.